Dry cell assembly



DRY CELL ASSEMBLY Filed Jan. 11, 1949 0ovn INSULAMR 101v PEMIEABLE I08 ssmmron ION EXCHANGE RES/N P r: I02

INVENTOR. EDGAR C PITZER Patented Aug. 19, 1952 Edgar C. Pitzer, Schenectady, N. Y., assignor to the United States of America as represented by the United States Atomic Energy Commission Application January 11, 1949, Serial No. 70,347

The present-invention relates toan improved filler composition for voltaic cells and to a voltaic cell-containingthis filler composition. 'll'he principle of the so-called dry cell is well known and the-construction of commerciat cells is fairly well standardized. As stated in the patent of Arsem, U. S. Patent Number 2,306,927, the commercial dry cell is made up as follows:-

A container of zinc serves as an anode; adepolarizing assembly serves as a cathode and is in the form of a core or bobbin made up of afiller composition containing carbon, manganese dioxide and a solution of zinc and ammonium chlorides, this core being mounted around .or in con-v tact with a carbon rod whichserves as a means of contact with the cathodic depolarizing assembly, and as an external electrode. The space between the cathode core and the zinc anode is filled with a filler composition in the form of a paste containing zinc and ammonium chlorides and a stifiening agent such .as starch or charcoal. In the ordinary dry cell the stiffening agent .contributes nothing to the performance of the cell butserves merely to keep the electrolyte in a semi-solid form or paste. V

During the operation of the cell the zinc electrode reacts with the ammonium chloride solution according to the equation,

As a result of the reaction the pH of the electrolyte increases and also basic zinc salts are formed. The effect of these reactions on the cell is a more rapid depletion of the cell than would occur in the absencevof these reactions. The inclusion of free acid in the paste does onset the harmful effects of such reactions to a small degree but it may also provide'the possibility of corrosion of the zinc electrode in which the paste is stored; a result which may be more harmful than the effects of the increase of pH. i

It is an object of the present invention to provide a voltaic cell capable of delivering more stable voltage under a sustained load.

It is another object ofthepresent invention to provide a 'filler composition for a voltaic'cell which increases the voltage stabilityand re coverability of the cell. M

It is a further object of the present invention to providea voltaic'cell which'quickly recovers its initial voltage after'a relatively shortus'e.

Itisa still further object of the present invention to provide a filler composition for a 'voltaic cell which minimizes the increase in the pH and the formation of basic zinc salts in the'cell.

. 2 Claims. (01. 136-83) Other objects of the present invention will be in part obvious and in part pointed-out hereinafter.

Referring to the drawing wherein a preferred arrangement of the elements of the present invention is illustrated, a carbon rod electrode H2 is, axially positioned inv a generally cylindrically shaped deposit H0 of manganese dioxide paste. This paste is formed by mixing finely divided manganese dioxide powder with sufficient. saturated, ammonium chloride solution to give the mixture a thick paste-like consistency. .The manganese dioxide paste isenveloped'on sides and bottom bya relatively thick paste .of ion exchange resin 1| 02 and separated from. said resin by a layer of unglazed cellophane N18. The resin paste, may be formed, for'example, by mixing 50 to 6.0 cubic centimeters of saturated ammonium chloride solution with each 100 grams of a base exchange resin, identified more fully below, said resin hav v ing jbeen pretreated with an acid such as hydrochloric acid. Twenty mesh resin is found suitable/for this, purpose. The resin paste is .con-. tained by and kept in electrical contact with a cylindrical zinc metal electrode I00 such as is conventionally used in dry cells. A coverof waxlike or plastic resist material I06 is provided on the upper surface of the paste layers so as to prevent evaporation of water therefrom.

A conventional external circuit may be attached toithe cell to measure the voltage and amperage produced. Thus, the zinc electrode may be connected through a conductor H4, the load H6, the milliameter H8, and the'conductor I20 to the carbon electrode H2, and a voltmeter may be connected between the conductors H4 and I28 to'meas-ure-the voltage developed between the electrodes; The current drawn from the" cell is measured'by means of the ,milliameter H8 connected in series-with the cell. r

The cell filled with the composition containing an ion exchange resin has a greater'volta'ge sta-, bility, particularly 'at relatively previously known cells. Such improvedcells are capable of quick recovery from higher loads of shortduration.

Inorder to illustrate the efliciency of operation of a cell provided by the present invention as compared with a conventional cell, the ntire anode 'assembly from a new andunused commercial cell such as is commonly used in flash l ghts was removed from its zinc cathode jacket and was inserted intact into a slurry composed of a base exchange. resin of a type which will be more fully identified, below and aqueous ammonium chloride solution. The slurry was conlow loads, than tional cells were identified as conventional cells No. l and No. 2 and the results obtained from these tests are listed in Table I. a

Table -,I

Dowex filled Cell Conventional Cell Conventional Cell No. 1 N o. 1 No. 2 Time, Minutes A We eas s voltage are We Gear that the resin-filled cell delivers a higher current at agreater voltage for a longer time than do conventional cells. Thus, it is seen that after onehalf hours steady idischarge through a ohmexternal resistance the resin-filled cell produced a voltage and current which. compared favorably-with the initial voltage and current produced'by conventional cells. I A second resin-filled cell,- 'dentified as, resinfilled cell No.12, was prepared and its recuperationfvoltage' immediately after a short, [circuit of the, cell whichjlasted for six minutes was compared with the recuperation voltage of two additional new and unused conventional cells which were individually short 'circuited for the same period of time. i The initial voltages and recuperat tion voltages of thesecells are listed in Table II.

Table II Initial Recuperation Voltage Voltage Resin-filled 0911 Nb. 2 ..'f 1; 95 1. Conventional Cell No. 3 1. 1.05 Conventional Cell No. 4 1. 1.00

. These results indicate that the; use of resin slurry of lthe type described below in conjunction with a conventional cellanode assembly; not only permits the maintenance of higher voltages at loads in the order of 10 ohms; but also indicate thatsuchresin-filled cells have higher recuperationvoltages than such conventional cells. qTheltheory of theoperation of'such a cell-is not fully understood. The following is 'oiiered asan explanation although it will be understood that the concept-of the invention is not to-be limited by the accuracy of thisexplanation.

Representing the acid form ofthe resin by H2R the reactions in the cell may be expressed Reaction (2) represents an equilibrium between the ammonium and hydrogen ions in the solution, the resin acting as an insoluble bufier. Reaction (3) removes zinc ions from the solution and also tends to resist changes in pH. Reaction (4) consumes ammonia produced by Reaction (1) When the resin is spent it will con- .tinue to serve as an inert filler, and will not interiere with the output of the cell. 1 l

The spent resin can be regenerated by digesting with dilute acid and thorough Washing with water.

A resin found suitable for use as a synthetic cation" exchange resin is sold under the trade name of Dowex 50. This product is an aromatic hydrocarbon polymer of the type described by I DAlelio in U. S. Patent 2,366,077, containing nuclear sulfonic acid groups as the sole ion active group at any pH value.

The resins suitable for use according to the present inventionareinot'limited to an aromatic hydrocarbon polymerqco'ritaining nuclear sulfonic acid groups such as Dowex'50, which is awalter insoluble sulfonated polymerizate 'of a' polyvinyl arylcompound. Anyion exchange resin capable of inhibiting the-rise of pH. of a substance ;s'us'-i ceptible to such a rise due to the formation there! in of basic cations, is suitable for this purpose.

Such other synthetic cation absorbers-as are described in the patentsv of DAlelio Numbers 2,340,110; 2,373,547; 2,373,548; 2,373,549; 2,366,-' 008 and others are also suitable for use according to the present invention, as are such resins as sulfonated petroleum coke; greensand 'aridisyn thetic inorganic zeolites. All of theion exchange resins'are preferably used in the acid form. In addition, other agents which inhibit the riseof pH of the cell as, for example, the nitrateor oxalate of urea may be employed in dilute mix-' ture with inert ingredients.

"Sincemany embodiments might be made of the present inventionandsince many changes might be made in theembodime'nt described, it is to be understood that the foregoing description is to be interpreted as illustrative only and'not in alimitingsense. Y

'Iclaimz r a 1. A voltaic dry cell comprising an inert anode, a,zinc cathode, a layer of a depolarizing paste consisting essentially of manganese dioxide and a saturated ammonium chloride solution ambient to said anode, a layer of resin paste in contact with said cathode, said paste consisting of a resin and saturated ammonium chloride solution, said resin being in'acid form and selected from the group consisting of sulphonated petroleum coke, greensand, synthetic inorganic zeolites, aromatic hydrocarbon polymers containing nuclear sulphonic'acid groups as the sole ion active group at'any pH value, and phenol'formaldehyde' desaturated ammonium chloride solution in paste iorm ambient to said anode, a layer of a resin paste containing about 5 'to"6 cubic centimeters of-- saturatedx'ammonium chloride solution for each 10 gramspf resin, said paste being in'c'on' tact with .said' cathode and said resin being selectedirom the groupjconsisting of sulphonated petroleum c'oke,'gree nsand, synthetic inorganic zeolites, aromatic hydrocarbon polymers contain? ing nuclear sulphonic acid-groups as thesole ion active group at any pH value, and phenol formaldehyde derivatives, and said layers being separated by and making electrical contact through an ion permeable separating member.

EDGAR C. PITZER.

REFERENCES CITED UNITED STATES PATENTS Name Date Young Apr. '7, 1942 Number Re. 22,065

Number Number Name Date Martus Apr. 20,1926 Heise Jan. 13, 1931 Heise Dec. 8, 1931 Heise Dec. 8, 1931 Heise June 28, 1932 Arsem Dec. 29, 1942 Ruben Mar. 8, 1949 FOREIGN PATENTS Country Date Great Britain Of 1905 Great Britain Mar. 23, 1933 

1. A VOLTAIC DRY CELL COMPRISING AN INERT ANODE, A ZINC CATHODE, A LAYER OF A DEPOLARIZING PASTE CONSISTING ESSNETIALLY OF MANGANESE DIOXIDE AND A SATURATED AMMONIUM CHLORIDE SOLUTION AMBIENT TO SAID ANODE, A LAYER OF RESIN PASTE IN CONTACT WITH SAID CATHODE, SAID PASTE CONSISTING OF A RESIN AND SATURATED AMMONIUM CHLORIDE SOLUTION, SAID RESIN BEING IN ACID FORM AND SELECTED FROM THE GROUP CONSISTING OF SULPHONATED PETROLEUM COKE, GREENSAND, SYNTHETIC INORGANIC ZEOLITES, AROMATIC 